(a) Field of the Disclosure
The present disclosure relates to a control method for a coolant control valve unit that cools coolant heated by an engine by using a radiator and controls coolant flow toward the radiator to reduce heat shock applied to the radiator.
(b) Description of the Related Art
Engines produce torque by burning a fuel and discharge thermal energy. A coolant absorbs thermal energy as it circulates through an engine, a heater, and a radiator, and releases the thermal energy.
Oil becomes highly viscous at low engine coolant temperatures. With thick oil, friction and fuel consumption increase, and exhaust gas temperatures rise gradually, lengthening the time taken for catalyst activation and causing deterioration in exhaust gas quality.
When the engine coolant temperature is excessively high, knocking may occur. If ignition timing is adjusted to suppress knocking, the engine performance may be degraded. In addition, excessive lubricant temperatures may result in poor lubrication because the viscosity becomes low.
However, one coolant control valve unit is used in specific regions of an engine, and is a valve that controls a number of cooling elements, such as keeping the coolant at high temperatures and other regions at low temperatures.
As an example of a conventional art, the coolant control valve unit includes a motor, a cam rotated by the motor, a rod moved by a profile formed at one surface of the cam, and a valve formed on the rod and having a structure opening and closing a coolant passage through the valve if the cam is rotated by the motor and the profile of the cam pushes the rod.
Meanwhile, to control temperature of the coolant, the coolant control valve unit controls a valve controlling coolant supplied to the radiator, and the valve is opened when the coolant temperature in a real time exceeds a target temperature. Here, hysteresis is applied to prevent often opening and closing operations of the valve.
For example, when the target temperature is 90 degrees Celsius, the hysteresis value is applied to 2 degrees during rising of temperature and the valve is opened at 92 degrees, and the valve is closed at 88 degrees during falling of temperature.
However, when the hysteresis value is fixed regardless of the driving condition, particularly when outside temperature is low, the coolant is rapidly cooled down due to repeated opening and closing operations of the valve, although the radiator coolant supply valve is opened in a short time.
Further, as the opening and closing operations of the valve repeats, low temperature coolant is supplied to the radiator so that heat exhaustion may be deteriorated and durability may be degraded. Further, durability of other cooling components as well as the radiator may be degraded.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.